Copper clad laminate (CCL) is a raw material for printed circuit board (PCB) which is the basis of the electronic industry and an indispensable important component for all kinds of electronic products. With the upgrading and replacement of electronic products, more and more PCBs are abandoned, and the harmful ingredients in these waste PCBs can pass into the environment through water, atmosphere, soil in natural conditions, causing potential, long-term harm to the environment. Moreover, these hazards are irreversible. Therefore, the waste PCBs must be recycled scientifically and reasonably. Recovery of waste PCBs has gradually become an emerging industry.
At present, the recovery of CCLs or PCBs in accordance with the principles can be divided into chemical recovery and physical recovery. The main methods include direct burial, incineration, pickling and cracking, etc. However, all these methods involve release of toxic substances, and easily result in secondary pollution to the environment, e.g. air or soil. Currently, the best international recycling method is the physical method, i.e. smashing first, then separating metal powder from non-metallic powder in a closed system with fan blowing on the basis of different proportions of metal and non-metal. Such method requires more smashes, and even the smashed powder needs to reach the micron level in order to ensure the separation of metal and non-metal. Moreover, such method has great energy consumption and noise, high equipment requirements and incomplete recovery.
CN1483754 discloses a chemical recovery method for a thermosetting epoxy resin composite material, using a strong nitric acid solution to degrade a thermosetting epoxy resin, which has a great corrosion to the container and a low recovery benefit. CN101519505 discloses a method for separating thermosetting epoxy resin or a composite material thereof by high temperature aqueous phase, which involves catalyzing the degradation of epoxy resin by using a heteropoly acid as a catalyst, and has a great influence on the performances of the recovered product.
Although degradable epoxy curing systems have been reported, the application thereof in CCLs has not been disclosed.
CN103249712A discloses synthetic degradable polyamine or polythiol, which can be used to cure epoxy resins and can be used in the field of carbon fiber composite materials. However, related compounding is needed if being applied to the field of CCLs. Degradable polyamine in the patent has a low curing activity. Curing accelerators, such as imidazoles, cannot be added in order not to affect its degradation performance, thereby leading to too long gelation time of the gel and being disadvantageous of the process control and curing of CCLs. Degradable polythiol has high curing activity, poor latency, and is not conducive to the application in the CCLs.